April 20, 2023
We are writing to express our views on the Agency for Healthcare Research and Quality’s (AHRQ) ‘living’ systematic review on cannabis and other plant-based treatments for chronic pain and subacute pain, update 2. The National Center for Health Research (NCHR) is a nonprofit think tank that conducts, analyzes, and scrutinizes research on a range of health issues, with particular focus on which prevention strategies and treatments are most effective for which patients and consumers. We do not accept funding from companies that make products that are the subject of our work, so we have no conflicts of interest.
Although we support the goals of the review and agree that there is a need for a systematic review of the effects of cannabis and other plant-based treatments for chronic pain, there are several important limitations of this report. We addressed these concerns after the draft systematic review was published in 2021. This updated review, which added two additional studies (one RCT and one observational study), does not remedy the following limitations.
- The vast majority of trials included in the systematic review were focused on patients with neuropathic chronic pain (61%), as was the case for the two newly included trials. Although AHRQ can’t improve the available data, the systematic review should be more explicit about the paucityof data on other types of chronic pain, including low back pain, osteoarthritis, fibromyalgia, and inflammatory arthritis. AHRQ should also emphasize that there is limited evidence on younger and older populations and important patient populations based on gender, race/ethnicity, or pregnancy/lactating status. If the goal of this report is to identify alternative treatments with equal or better benefits for pain for all patients, then this exclusion of large groups of patients should be emphasized, explaining that the scope of the review is limited to a specific patient population. Otherwise, the results will be misleading to those who rely on the review to aid in their decision-making.
- The review should emphasize that study durations were short-term (many only 4-6 weeks long), and they included less than 6 months follow-up, and that those with chronic pain often seek long-term treatments that they will use for years. Short studies are not an adequate basis from which to draw conclusions about the long-term use of cannabinoids for chronic pain management. Although the limitation due to short-term studies is acknowledged in the review, it should be more explicitly emphasized so that readers quickly skimming the review or only reading the section on conclusions are made aware of this limitation.
- The inconsistent nomenclature also represents a serious limitation that the report should emphasize. As the draft review states, several studies only describe products as “extracted” without giving additional information of the purity of the studied end product or as to how the product was extracted. Not only does this severely limit the interpretation of the evidence cited in this review, it also seriously hampers health care providers and patients’ ability to find information and choose the right treatments for them.
- As we stated in 2021, the title of the draft report is misleading. The current title is “Living Systematic Review on Cannabis and Other Plant-Based Treatments for Chronic Pain and Subacute Pain.” “Subacute pain” was added to the title as the inclusion criteria were expanded to also address subacute (4 to 12 weeks’ duration) pain and adolescents. However, no studies evaluated adolescents or cannabis for subacute pain. Further, the review contains no research on other plant-based treatments such as kratom, and neither of the two additional studies remedy this deficiency. While we appreciate the inclusion of the new RCT that reports on synthetic high THC to CBD ratio products and low-THC to CBD ratio products versus placebo, this report still has insufficient evidence of outcomes assessing benefits on high THC to CBD ratio products extracted from whole-plant cannabis, whole-plant cannabis products, or low THC to CBD ratio products such as topical CBD. The review is much more limited in scope, focusing on treatments such as comparable THC to CBD ratio oral spray. The title of the review should therefore more accurately reflect the narrow range of cannabinoid products covered by the review; otherwise, it is inaccurate and misleading to those who will turn to it for medical information and to aid in decision making.